Our goal is to develop new drugs in order to improve the outcomes of patients with neuroblastoma (NB). These cancers are the most common malignant sympathetic nervous system tumors of childhood. They originate from the neural crest and are biologically heterogeneous tumors while some tumors undergo spontaneous regression or differentiation. The majority of these tumors grow aggressively, metastasize and remain resistant to multimodal therapy; less than 20% of patients with advanced disease survive. Despite current aggressive treatment strategies employing intensive myeloablative chemotherapy with autologous bone marrow transplantation, most patients with high risk (Stage 4) NB die of their disease. Eradication of refractory microscopic disease remains one of the most significant challenges in the treatment of high-risk neuroblastoma. In order to improve the outcome for patients with this disease, there is an urgent need to develop new drugs. Similar to other solid tumors, NB is known to produce growth factors promoting angiogenesis. Targeting angiogenesis in addition to the tumor has shown considerable success in the treatment of several solid tumors. Our recent efforts have lead to the development of bromoacetoxycalcidiol (B3CD) a non-calcemic, 3- bromoacetoxy-ester derivative of calcidiol, as a cytotoxic agent that targets cancer cells and angiogenesis. In our preliminary studies B3CD, inhibited the proliferation of neuroblastic cells and endothelial cells (critical for angiogenesis). B3CD increased caspase-3 activity, rapidly induced apoptosis rapidly in neuroblastic and endothelial cells and inhibited angiogenesis. Furthermore, administration of B3CD to SCID mice over a period of 28 days did not cause any toxicity or increased serum calcium levels indicating a lack of apparent general toxicity. Based on these observations, we hypothesize that B3CD acts as a novel therapeutic agent in NB by inducing apoptosis and inhibiting angiogenesis. We propose to (a) further examine these initial observations of cytotoxic activity of B3CD in NB cells with particular emphasis on delineating cellular pathways involved in its mechanism of action (particularly leading to growth inhibition and apoptosis), (b) determine the anti-angiogenic activity of B3CD by ascertaining its effect on endothelial cell proliferation, migration, tube formation, aortic ring sprouting and chick chorioallantoic membrane (CAM) vascularization, and (c) to determine the in vivo efficacy of B3CD in mouse xenograft model of human NB. The knowledge gained from the study of bromoacetoxycalcidiol, a novel non-toxic calcidiol derivative, is expected to help design innovative treatments for pediatric patients with NB in general and high-risk NB in particular. B3CD could potentially be used alone or in combination with standard chemotherapy to treat this devastating illness. [unreadable] [unreadable] [unreadable]